Dr Penny Spikins, from the University of York, suggests a desire to prove their trustworthiness, rather than a need to demonstrate their physical fitness, was the driving force behind the fine crafting of hand-axes by Homo erectus/ergaster in the Lower Palaeolithic period.
The theory contrasts sharply with previous claims that finely crafted hand-axes were about competition between males and sexual selection.
Dr Spikins says: "Since their first recovery, the appealing form of hand-axes and the difficulty of their manufacture have inspired much interest into the possible 'meaning' of these artefacts".
Hand-axes, or bifaces, appeared around 1.7 million years ago in Africa and spread throughout Africa, Europe and western Asia, functioning primarily as butchery implements. Hand-axe form remained remarkably similar for more than a million years.
"The form of a hand-axe is worth considerable effort, as it may demonstrate trustworthiness not only in its production, but also each time it is seen or re-used, when it might remind others of the emotional reliability of its maker."